1. Technical Field
The present invention relates generally to imaging devices and more particularly to a device for monitoring the condition of a toner filter assembly for an imaging device.
2. Background Art
The process of electrostatic imaging, whether in an electrophotographic copier, a laser printer, or another imaging device, typically involves the light-directed distribution of electrostatic charge over the surface of a photoconductor. A developing system deposits toner particles on the photoconductor and the toner particles are in turn deposited as an image onto a sheet of paper. In order to prolong the life of an imaging system, imaging systems typically, use replaceable assemblies including consumable elements of the imaging system such as toner and wear-sensitive elements including developing systems and photoconductors.
During the imaging process, toner particles may become airborne and deposit undesirably within the imaging system or may escape the imaging system entirely. Loose toner can create print quality problems, clog replaceable and non-replaceable moving parts within the imaging system, and contaminate the environment outside the imaging system. Attempting to clean loose toner out of an imaging device is difficult and may damage fragile parts within the imaging system. An imaging device may therefore include a filter assembly which removes toner particles from the air circulating within the imaging system. Similarly, a replaceable toner cartridge or developer assembly may also include a filter assembly which removes toner particles from the air circulating within the imaging system. A loss of toner may also occur if elements within a toner cartridge or developer assembly, such as toner seals, break. Breakage is more common when the toner within the toner cartridge or developer assembly is refilled or, if many images requiring little toner are printed, and the lifetime of the moving parts within the developer assembly expires before toner levels dwindle. This may lead to breakage of toner seals or other parts. Toner spillage due to breakage rapidly clogs the filter assembly. Over the life of a toner cartridge or developer assembly, toner can clog the filter assembly even without a breakage event. In either case, the clogging of the filter assembly may go unnoticed by the user, inadvertently degrading the performance of the imaging device.
Therefore, it may be advantageous to provide a device for monitoring the condition of imaging device air/toner filter assemblies. It may also be advantageous to prevent usage of the imaging system if the toner filter assembly is clogged. There may also be an advantage in providing for a qualitative estimate of filter life that may also aid in detecting toner seal leakage or breakage if filter blockage increases more quickly than normal.
The present invention is directed to a device for monitoring an air transport efficiency of an air/toner filter element for an imaging device. The device employs an optical sensing device to monitor a concentration of toner particles in the filter element. The air/toner filter element may be installed in a wall of an imaging device housing or in the alternative it may be incorporated directly in a toner cartridge or developer assembly. In a preferred embodiment, the optical sensing device monitors a concentration of toner particles captured in a filter element. The optical sensing device is connectable to an output or display for displaying data representative of an air transport efficiency of the filter element. The output may indicate that the filter element exhibits a predetermined condition, for instance that the filter element is functioning with an air transport efficiency of a measured percentage of full efficiency. According to the present invention, the optical sensing device determines filter element status by detecting the optical characteristics of the filter element. A relatively clean filter element will exhibit greater transmission of light indicating a relatively greater air transport efficiency. Conversely, a clogged filter element will be darker and more opaque due to the toner trapped within it indicating a relatively lesser air transport efficiency.
In a preferred embodiment of the invention, the optical sensing device is electrically connected to an imaging device controller. When a condition which indicates clogging of the filter element is detected by the optical sensing device, the controller may disable the imaging device to prevent inadvertent use of a defective toner cartridge assembly. Additionally, or in the alternative, the imaging device controller output may enable a signal in the form of a sensory output, i.e. a visual or audible signal. Alternately, the imaging device output from the controller may be in the form of a message displayed on a video output device of an attached or networked computer. This obviates the need for the user to inspect or monitor the optical sensing device directly.
In one embodiment of the invention, the optical sensing device includes an optical element which measures the amount of light that can pass through the filter element, determining its translucency. In another embodiment of the invention, the optical element measures the reflectivity, or lightness and darkness, of the filter element surface. An optical element senses the degree of blockage of the filter element as a function of the amount of light being sensed by the optical element. Alternatively, the optical sensing device may simply sense and determine a binary pass/no-pass determination, once again, as a function of the amount of light being sensed by the optical element.
An optical sensing device may operate based on a change in reflectance of light from a source to a receptor. For sensor applications, photodetector arrays require the objects they sense to be illuminated by some means. An illumination source is directed at an object, in this case the filter element, and the optical sensing device is positioned relative to the illumination source and the filter element to permit sensing of either the amount of light that passes through the filter element or, in the alternative, the sensing device senses reflectivity of an illuminated surface of the filter element. The optical element may sense both the level and the rate of filter element blockage. If the filter element begins to plug quickly, it can be assumed that excessive toner is leaking from the cartridge through the seals and the imaging device may be disabled before excessive toner is released into the printer imaging device.